The invention relates generally to a battery charge and discharge control system for vehicles such as boats, RV's and the like, and more particularly to an ignition controlled multiple battery charge and discharge system for boats.
In recent years, there has been increased use of electrical systems as a prime source for motive power in trolling, and as a source of power for accessories. Automobile-type 12 volt electrical power systems are mainly what is used and commercially available for fishing crafts to provide the electrical power needed.
Boat users have found, in some cases, that a more efficient utilization of power is achieved at a voltage that is higher than that of the standard 12 volt system. To solve this problem, boat users began combining two or more batteries in series to obtain multiples of the 12 volts obtained from standard batteries. These practices have been furthered by manufacturers introduction and offering of 24 volt or combinations of 12 or 24 volt trolling motors. These motors are most likely to be powered by multiple 12 volt batteries.
Along with the practice of using multiple 12 volt batteries comes the problem of how to charge them. Although these batteries are connected in series during use to yield multiples of 12 volt output, they must be connected in parallel during charging. In the past, boat users have had to physically disconnect the combined series of batteries and connect them in parallel, or manually flip a switch that controls series and parallel connection.
In most cases, the boat or RV has a main battery connected to the generator or alternator of an engine. To charge the accessory 12 volt batteries, they are placed in parallel with the main battery. As mentioned above, series and parallel connections have been performed both physically and manually. The problem with these methods is that they are time consuming and leave open the possibility for human error. This would be especially true for a fisherman who needs to make the appropriate connections but has no daylight or battery power to yield the appropriate light to make the necessary connection. There is a need for an automatic control system that eliminates the need for physical and manual connection of batteries. There is a need for a system that automatically isolates the main battery from a series connection with the auxiliary batteries to allow the auxiliary batteries to discharge without affecting the voltage of the main battery.
Another problem associated with physical and manual connection of multiple 12 volt batteries is that when the batteries are not being charged and are in series, there is the possibility of draining all of the electrical power in main battery as well as in the auxiliary batteries. To overcome this problem, the main battery would need to be isolated from the auxiliary batteries, so that the auxiliary batteries can be discharged without affecting the voltage level in the main battery. Isolation insures that electrical power will be available when the engine needs to be started. In the past, the task of isolating the main battery would be performed physically, or manually by way of a control switch. Again, these methods of isolating the main battery are time consuming and leave open the possibility for human error.
A number of electronic circuits have been developed to provide manual dual battery switching systems. One such device is disclosed in U.S. Pat. No. 4,114,082 to Sheilder (issued Sep. 12, 1978). The Sheilder circuit is used on a pair of batteries of equal voltage rating and connects them together in parallel through isolation rectifiers and in series through an electronic switch.
The problem that fishermen encounter through the use of the Sheilder circuit is the error that may result from manual engagement of the circuit. In addition, the Sheilder circuit uses Silicon Control Rectifiers and diodes for isolation of the batteries, which prevents them from ever attaining full charge, due to the voltage drop across the diode. There is a need for a system that can isolate batteries during discharge, and provide full charge to those battery during charging.
Further, there is a need for a system that can provide 100% charging to batteries that are not of an equal voltage rating. Ideally, the system would allow for parallel charging of each battery up to its maximum charging potential, and upon reaching that battery's maximum charging potential, charging is discontinued. Parallel charging of the remaining batteries will be continued until each individual battery's maximum charging potential has been reached.
In particular, this feature would be helpful where boat users chose to use "deep cycle" batteries as auxiliary batteries and lead acid batteries for the main battery. A system that could provide maximum charging of all batteries having different voltage ratings would eliminate the possibility of overcharging one battery and undercharging another.